qmail is an outstanding example of a fast, reliable,
secure piece of system software---something that is all too rare in
this sad, fallen world. By studying how it works, we can learn
something about how to make all software better. This talk offers a
brief overview of the structure of the qmail system and its
principal components, looking briefly at several major design
decisions that underlie qmail's success as a safe, efficient,
reliable, and secure package.